It is well known to facilitate the handling of unitised and unit loads by carrying them on a pallet.
Such pallets may be of steel, plastic, aluminium or composites of different materials such as fibreboard with plastic; but are mainly of timber, to provide the strength to support the load and as spaces suitable for use with mechanical handling equipment such as lift truck forks, pallet trucks, conveyors, and slings.
When these pallets are designed to provide the strength, quality, accuracy, dimension, shape and material best suited to the products, handling equipment, racking and procedures at a particular location, then such features are indispensable to the efficient operation of the handling system.
However, in designing for in-house functions features are used in the pallets which render them undesirable for use in transporting loads to other locations.
It is often the case that the pallet used in transit:
(a) Adds significantly to the dead weight of a shipment.
(b) Reduces the effective volume utilisation of the carrier vehicle.
(c) Adds to shipment cost per unit of product.
(d) Is of high cost to provide strength, quality, accuracy requirements.
(e) Needs replacements to maintain the pallet supply.
(f) Has to be returned.
(g) can get lost on return.
(h) May not be dimensionally compatible with transport vehicles and/or destination handling and storage systems.
(i) May be made of a material which is not compatible with a particular mixed transit load or legal requirement at destination. e.g. certain chemicals on an aluminium pallet or timber pallets not satisfying pest control requirements.
Practices within the existing art include:
Accepting the known inefficiencies, high costs and loss risk, but transporting goods on in-house pallets anyway.
Stripping loads from their pallets and loading by hand to vehicles and containers. This practice is very arduous both at desptach and receipt location; a disadvantage which is compounded by costs incurred due to time taken through poor labour utilisation and overdue turn around time of transportation units.
Use of one trip timber pallets. These are weaker, lighter and cheaper than `normal` or special ones, but are still poor in space utilization and still incur weight and cost penalties, albeit reduced.
Use of composite pallets; such as fibreboard/plastic, fibreboard/polystyrene etc; which although effective in respect of lightness of weight and reduced cost, lose out on space utilisation and strength.
Use of slip sheets; which are excellent, where applicable, in space utilisation, costs and strength characteristics and are re-cycleable. However they can only be handled by lift trucks which are fitted with special purpose "push-pull" attachments.
This means that such attachments must be in use at all despatch and reception locations. They are expensive; they have the effect of reducing the turning circle of the truck; the attachment downrates the safe lifting load rating of the truck, which means larger and heavier trucks are needed than normally acceptable for given weights of loads; and they require significant operator training and skill.
Further, in stacks more than one load high, the slip sheet operation involves the load being handled skidding over the top of the one upon which it is resting, whilst the uninterrupted space between sheets and vertical loads is not acceptable for transport of perishable goods requiring through ventilation.
It has been proposed to form pallets from fibreboard material affording low cost and being discardable at the destination, and in addition collapsible pallets of such material have been proposed, see U.S. Pat. Nos. 2,702,682 and 3,167,038. In the latter patent the pallet is collapsed after use manually and similarly erected prior to use manually and the intention is to afford ready storage when out-of-use. The pallet is not adapted to open on entry of fork lifts and thereafter collapse. In the former patent a folded fibreboard material is used for the legs but this does not expand in use and forms merely a convenient construction for varying the height of the base during manufacture.
In British Pat. No. 696,214 a pallet is disclosed for four-way entry this having U-shape channels of metal which are not intended to collapse. None of the prior discloses or suggests a lightweight construction of pallet having the capability of supporting a heavy load but which nevertheless can also accept fork lift entry through an expansion action. All the aforementioned prior-art is concerned with maintaining at all times sufficient space for clean-entry of the forks of a fork-lift truck.